﻿#region Copyright & License

//
// Author: Ian Davis <ian.f.davis@gmail.com> Copyright (c) 2007-2008, Ian Davs
//
// Portions of this software were developed for NUnit. See NOTICE.txt for more
// information. 
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may not
// use this file except in compliance with the License. You may obtain a copy of
// the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
// License for the specific language governing permissions and limitations under
// the License.
//

#endregion

#region Using Directives

using System;
using Ensurance.Properties;

#endregion

namespace Ensurance.Constraints.Type
{
    /// <summary>
    /// InstanceOfTypeConstraint is used to test that an object is of the same
    /// type provided or derived from it.
    /// </summary>
    public class InstanceOfTypeConstraint : TypeConstraint
    {
        /// <summary>
        /// Construct an InstanceOfTypeConstraint for the type provided
        /// </summary>
        /// <param name="type"></param>
        public InstanceOfTypeConstraint(System.Type type)
            : base(type)
        {
        }

        /// <summary>
        /// Test whether an object is of the specified type or a derived type
        /// </summary>
        /// <param name="actual"></param>
        /// <returns></returns>
        public override bool IsSatisfiedBy(System.Type actual)
        {
            Actual = actual;
            return actual != null && ExpectedType.IsInstanceOfType(actual);
        }

        /// <summary>
        /// Write a description of this constraint to a MessageWriter
        /// </summary>
        /// <exception cref="ArgumentNullException">if the message writer is null.</exception>
        /// <param name="writer"></param>
        public override void WriteDescriptionTo(IMessageWriter writer)
        {
            if (writer == null)
            {
                throw new ArgumentNullException("writer");
            }
            writer.WritePredicate(Resources.InstanceOf);
            writer.WriteExpectedValue(ExpectedType);
        }
    }
}
